Integrating algaculture into small wastewater treatment plants: process flow options and life cycle impacts

Abstract

Algaculture has the potential to be a sustainable option for nutrient removal at wastewater treatment plants. The purpose of this study was to compare the environmental impacts of three likely algaculture integration strategies to a conventional nutrient removal strategy. Process modeling was used to determine life cycle inventory data and a comparative life cycle assessment was used to determine environmental impacts. Treatment scenarios included a base case treatment plant without nutrient removal, a plant with conventional nutrient removal, and three other cases with algal unit processes placed at the head of the plant, in a side stream, and at the end of the plant, respectively. Impact categories included eutrophication, global warming, ecotoxicity, and primary energy demand. Integrating algaculture prior to activated sludge proved to be most beneficial of the scenarios considered for all impact categories; however, this scenario would also require primary sedimentation and impacts of that unit process should be considered for implementation of such a system.

Evaluating Removal of Steroid Estrogens by a Model Alga as a Possible Sustainability Benefit of Hypothetical Integrated Algae Cultivation and Wastewater Treatment Systems

“…This likely happens for two reasons: (1) Different estrogens have different SPE recovery efficiencies (estrone >17α-estradiol >17β-estradiol, data not shown). (2) Estrogens with very short half-lives could be degraded during the extraction process (e.g., 17β-estradiol). Despite these differences in initial measured concentrations, the experimental results are useful for evaluating the efficiency and pathway of removal for each estrogen.…”

“…1,2 Integration of algaculture into wastewater treatment has been suggested as one means of creating bioenergy while also efficiently "recycling" aqueous nitrogen (N) and phosphorus (P) from treated effluents, thereby reducing downstream eutrophication. 3−6 Separately, discharge of steroid hormones and their structural analogs is a critical environmental concern because these "environmental estrogens" can impair the reproduction and development of aquatic wildlife even at very low concentrations (10−100 ng/L).…”

Anaerobic Digestion of Algae Biomass to Produce Energy during Wastewater Treatment

“…Sturm and Lamer (2011) estimated a 60% reduction in WRRF energy consumption following implementation of algae-based nutrient treatment, arising from both digestion of algae biomass and reduced energy consumption for nitrogen and phosphorus removal. Steele et al (2014) evaluated three possible WRRF adaptions incorporating algae cultivation. The best performance was observed for use of the algae pond to treat primary effluent, delivering a 60 to 80% reduction in energy use compared to the baseline WRRF configuration.…”

“…None of the analyses by Sturm and Lamer (2011), Steele et al (2014), and Beal et al (2012) specifically accounted for anaerobic digestion of the algae biomass to produce electricity. Sturm and Lamer (2011) evaluated direct combustion and processing into biodiesel as possible algae conversion options.…”

Evaluating Algae-mediated Removal of Ciprofloxacin

“…In this vein, there has been recent interest in the development of wastewater treatment technologies that are both net energy-generating and have the capacity to remove ECs (Zhang et al, 2014;Ottmar, 2010;Ottmar et al, 2013;McCarty et al, 2011;Steele et al, 2014;Peng and Colosi, 2016). The synergy between algae cultivation and sewage treatment is especially interesting considering that algae utilize nitrogen and phosphorus, which are costly nutrients for algae farms to supply, to undergo photosynthesis and WWTPs have an abundance of these nutrients and are required to remove them.…”